Not applicable.
The present invention relates to an apparatus for illuminating an interior space by transferring light from a source through a wall.
Since the advent of the electric light bulb and readily available electric power, most buildings have been designed with the assumption that interior spaces will be illuminated by artificial lights. However, this assumption has been challenged for several reasons. First, the broader spectrum of natural sunlight is better suited to visual tasks. In addition, natural lighting provides more balanced color which is aesthetically pleasing. Further, reducing the use of artificial lights can substantially reduce energy consumption. Not only is energy consumption reduced by an amount necessary to produce the required illumination but the amount of heat released into the interior space can also be substantially reduced, reducing the consumption of energy for cooling.
The use of windows and skylights to provide ventilation and admit natural heat and light to interior spaces of buildings is an ancient practice. While windows and skylights facilitate the entry of natural light and heat, they also have several disadvantages and limitations. Skylights are only practical if there is access to the roof from the interior space. Further, skylights typically require complex roof framing and construction of a tunnel for light to pass from the roof to the ceiling of the interior space. In addition, sky lights are prone to water leakage.
A window permits light and heat to be transferred through a vertical wall into an interior space. Like skylights, windows require special framing around the opening in the wall and altering the framing to add or enlarge a window in a wall of an existing structure can be expensive or impractical. In addition, the efficiency of windows is fairly low. Windows permit light striking the vertical plane of the wall, either transmitted directly from the source or reflected from the environment, to transit the wall. Since windows do not concentrate the light, a substantial window area is required to provide good illumination. In addition to complicating construction, a large window area results in substantial heat gain and loss to the interior space. Higher thermal efficiency can be obtained with complex windows having several layers of specially coated glass separated by a special gas. However, these windows are expensive and difficult to install.
Several devices have been developed to-enhance the solar illumination performance of windows. For example, Eijadi et al., U.S. Pat. No. 4,593,976 discloses a solar illumination device comprising a pair of convex mirrors arranged on the outside of a wall that collect and focus light on a vertical window. In addition, Howard, U.S. Pat. No. 4, 630,892, discloses a device that may be mounted on a wall or a roof of a building to track the sunlight and project it through a window into the structure. These devices increase the amount of sunlight transferred to the interior space through a window by concentrating solar energy on the window. However, the light is still transferred into the interior space through a window subject to the limitations and disadvantage of conventional windows. For example, the special framing required for the window opening may make adding a window or increasing the size of a window expensive or impractical.
What is desired, therefore, is a compact, easily installed system for directing light from a light source through a wall to illuminate an interior space.